JP2006302742A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of detecting an operation state of an on-off valve installed in a connection passage connecting a fuel gas supply passage and an oxidant gas supply passage in the upstream part of the fuel cell. <P>SOLUTION: The fuel cell system 1A is equipped with a fuel cell 10 generating electric power with a hydrogen gas supplied to an anode 12 and a humidified air supplied to a cathode 13, a hydrogen gas supply passage through which hydrogen gas to be supplied to the anode 12 flows and a humidified air supply passage through which a humidified air to be supplied to the cathode 13 flows, the connection passage connecting the hydrogen gas supply passage and the humidified air supply passage, the on-off valve 42 installed in the connection passage, and a hydrogen sensor 32, and the hydrogen sensor 32 is positioned in piping 31a on the cathode 13 side from the on-off valve 42 and the upstream side of the fuel cell 10. The fuel cell system 1A detects the hydrogen gas supplied to the anode 12 which is a counter electrode of the cathode 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  In recent years, a fuel cell stack (fuel cell) in which a plurality of single cells are stacked has been actively developed as a power source for fuel cell vehicles. When a fuel cell generates electricity, water is generated mainly on the cathode (air electrode) side. Part of the generated water diffuses in the solid polymer electrolyte membrane (hereinafter referred to as electrolyte membrane) constituting the single cell and permeates to the anode (fuel electrode) side. Further, in order to maintain the wet state of the electrolyte membrane, a method of supplying humidified air (oxidant gas) to the cathode side is generally employed.

  Thus, the water content of the gas flowing through the fuel cell is high due to water generated by power generation and humidification. Therefore, when the temperature of gas falls, the water contained in gas will condense. Therefore, when the fuel cell is used in the winter or in a cold region, if the fuel cell is exposed to below freezing after being stopped, the inside of the fuel cell may freeze.

Therefore, in order to prevent freezing in the fuel cell, a connection channel that connects the fuel gas supply channel and the oxidant gas supply channel is provided on the upstream side of the fuel cell, and an open / close valve is provided in the connection channel. Has been proposed to open the on-off valve when the fuel cell is stopped and supply scavenging gas (non-humidified air) from the compressor to both the anode and cathode of the fuel cell. (See Patent Document 1). That is, the scavenging of the fuel cell is to push out water or the like generated by the power generation by the scavenging gas, and is also called an air purge.
Japanese Patent Laying-Open No. 2003-331893 (paragraph numbers 0012 to 0033, FIG. 1)

  However, during normal power generation of the fuel cell, for example, if hydrogen gas is supplied to the cathode of the fuel cell because the valve is not closed, the output of the fuel cell is reduced. There is a desire to detect whether or not it is operating.

  Accordingly, the present invention provides a fuel cell system capable of detecting the operating state of an on-off valve provided in a connection channel connecting the fuel gas supply channel and the oxidant gas supply channel upstream of the fuel cell. This is the issue.

  As means for solving the above-mentioned problems, the invention according to claim 1 is directed to a fuel cell that generates power by supplying a fuel gas to the anode and an oxidant gas to the cathode, and a fuel to be supplied to the anode. A fuel gas supply channel through which gas flows, an oxidant gas supply channel through which oxidant gas supplied to the cathode flows, and a connection that connects the fuel gas supply channel and the oxidant gas supply channel A flow path, an open / close valve provided in the connection flow path, and a gas detection means, and the gas detection means is located on at least one side of the anode and the cathode from the open / close valve and has a counter electrode The fuel cell system is characterized in that it is a type of sensor capable of detecting the gas supplied to the fuel cell.

  According to such a fuel cell system, for example, as described in an embodiment described later, the gas detection means is a hydrogen sensor, and the hydrogen sensor is located on the cathode side from the on-off valve, and is opposed to the cathode. In the case of a sensor that detects hydrogen gas supplied to an anode (see FIG. 1), the hydrogen sensor detects hydrogen gas even though a close command is sent to the on-off valve to close the valve. In such a case, the operating state can be detected when the on-off valve is not operating well, that is, it is not closed well and the on-off valve is out of order.

  The invention according to claim 2 is the fuel cell system according to claim 1, wherein the gas detection means is located upstream of the fuel cell (fuel gas and oxidant gas supply side). .

  According to such a fuel cell system, the gas passing through the on-off valve can be detected by the gas detection means before being diluted by the fuel cell. Thereby, the operating state of the on-off valve can be detected satisfactorily.

  According to the present invention, there is provided a fuel cell system capable of detecting an operating state of an on-off valve provided in a connection channel connecting a fuel gas supply channel and an oxidant gas supply channel upstream of the fuel cell. be able to.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2 as appropriate. FIG. 1 is a configuration diagram of a fuel cell system according to the present embodiment. FIG. 2 is a flowchart set in the fuel cell system according to the present embodiment.

≪Configuration of fuel cell system≫
As shown in FIG. 1, a fuel cell system 1A according to the present embodiment is a system mounted on a fuel cell vehicle, and includes hydrogen gas (fuel gas, reaction gas) on a fuel cell 10 and an anode 12 of the fuel cell 10. ), A cathode system 30 that supplies and discharges humidified air (oxidant gas, reaction gas) to the cathode 13 of the fuel cell 10, and the anode system 20 and cathode on the upstream side of the fuel cell 10. A scavenging gas introduction system 40 (connecting system) that connects the system 30 and introduces scavenging gas (non-humidified air) from the cathode system 30 to the anode side of the anode system 20 when scavenging the fuel cell 10 is controlled. ECU 50 (Electronic Control Unit, control device). The scavenging time of the fuel cell 10 is when the power generation of the fuel cell 10 is stopped or when power generation is started. That is, in the case of a fuel cell vehicle, the scavenging time of the fuel cell 10 is when the ignition switch (IGSW) is turned on or off.

<Fuel cell>
The fuel cell 10 (fuel cell stack) mainly includes a membrane electrode assembly (MEA) formed by sandwiching both surfaces of a monovalent cation exchange type electrolyte membrane 11 between an anode 12 (fuel electrode) and a cathode 13 (air electrode). : Membrane Electrode Assembly, membrane electrode assembly) and a plurality of single cells composed of separators sandwiching the MEA. In the separator, a groove for supplying hydrogen gas and humidified air to the entire surface of the electrolyte membrane 11, a through-hole for supplying each single cell, and the like are formed in a complicated manner. When hydrogen gas is supplied to the anode 12 and humidified air is supplied to the cathode 13, a potential difference is generated in the membrane electrode assembly, and power demand from an external load such as a travel motor connected to the output terminal of the fuel cell 10 is obtained. In response to this, the fuel cell 10 generates power.

<Anode system>
The anode system 20 is a system that supplies / discharges hydrogen gas to / from the anode 12 of the fuel cell 10. Hereinafter, the hydrogen gas supply side and the hydrogen gas discharge side of the anode system 20 will be described in this order.

<Anode system-hydrogen supply side>
The hydrogen supply side of the anode system 20 mainly includes a hydrogen tank 21 in which hydrogen gas is stored, a shut-off valve 22, and an ejector 23 toward the downstream side (fuel cell 10 side). The hydrogen tank 21 is connected to the shut-off valve 22 via a pipe 21a, and the shut-off valve 22 is connected to the ejector 23 via the pipe 22a. The ejector 23 is connected to a fuel supply port 12a that communicates with the anode 12 of the fuel cell 10 via a pipe 23a. The piping 22a is provided with a pressure reducing valve (not shown). The shutoff valve 22 is electrically connected to a control unit 51 of the ECU 50 described later, and the control unit 51 opens / closes the shutoff valve 22 as desired.
Therefore, when the shut-off valve 22 is opened, the hydrogen gas is depressurized from the hydrogen tank 21 to be supplied to the anode 12 of the fuel cell 10.
In the present embodiment, the hydrogen gas supply channel (fuel gas supply channel) through which the hydrogen gas supplied to the anode 12 circulates is a pipe 21a, a shut-off valve 22, a pipe 22a, an ejector 23, and a pipe. 23a (fuel gas supply channel means).

<Anode system-Hydrogen discharge side>
The hydrogen discharge side of the anode system 20 mainly includes a gas-liquid separator 24, a hydrogen purge valve 25 (scavenging valve), and a diluter 26 for diluting unreacted hydrogen gas.

The gas-liquid separator 24 (catch tank) is a device for gas-liquid separation of gas discharged from the anode 12 of the fuel cell 10 (hereinafter referred to as anode offgas) and removing water in the anode offgas. The gas-liquid separator 24 is connected to the downstream side of the fuel discharge port 12b communicating with the anode 12 of the fuel cell 10 via a pipe 24a.
In addition, the gas-liquid separator 24 includes a refrigerant pipe (not shown) through which a refrigerant flows, and the anode off-gas introduced therein is cooled to a predetermined level via the pipe 24a so that unreacted hydrogen gas and Gas-liquid separation with water. However, the gas-liquid separation method of the gas-liquid separator 24 is not limited to this, and may be a method of separating by a centrifugal force, for example.

  The downstream side of the gas-liquid separator 24 is connected to the ejector 23 via the pipe 24b and to the diluter 26 via the pipe 24c. The pipe 24b is provided at an appropriate location (such as the upper wall) of the gas-liquid separator 24 so that the separated unreacted hydrogen gas is returned to the ejector 23 and the hydrogen gas is circulated. The pipe 24c is provided at an appropriate position (such as the bottom wall) of the gas-liquid separator 24 so that the separated water (liquid) is discharged. The pipe 24c is provided with an opening / closing valve 28. By appropriately opening / closing the opening / closing valve 28, water accumulated in the gas-liquid separator 24 is sent to the diluter 26 as drain water.

  The hydrogen purge valve 25 is an on-off valve, and its upstream side is connected to a midway position of the pipe 24b via the pipe 25a. The downstream side of the hydrogen purge valve 25 is connected to the diluter 26 via a pipe 25b. The hydrogen purge valve 25 introduces a scavenging gas from the cathode system 30 to the anode system 20 when the amount of impurities (water or nitrogen gas) in the circulating hydrogen gas becomes high (at the time of hydrogen purging) or in the fuel cell 10 Opened when scavenging.

The diluter 26 (dilution box) is a device having a dilution space inside, and dilutes the anode off gas containing unreacted hydrogen gas supplied from the pipe 25b at the time of hydrogen purge when the hydrogen purge valve 25 is opened. It is like that. The upstream side of the diluter 26 is connected to a pipe 24c and a pipe 31b in addition to the pipe 25b.
On the downstream side of the diluter 26, a pipe 26a for discharging drained water containing diluted hydrogen gas and water introduced into the diluter 26 after being separated by the gas-liquid separator 24 is provided at an appropriate position. ing.

<Cathode system>
The cathode system 30 is a system that supplies and discharges humidified air (non-humidified air at the time of scavenging) to the cathode 13 of the fuel cell 10, and mainly includes a compressor 31 (pump) and a hydrogen sensor 32 (gas detection means). In preparation.

<Cathode system-Air supply side>
The air supply side of the cathode system 30 will be described. The compressor 31 is a device that takes in outside air, compresses it, and sends it to the cathode 13. The compressor 31 is connected to an air supply port 13a that communicates with the cathode 13 of the fuel cell 10 via a pipe 31a. Further, the pipe 31a is provided with a humidifier (not shown) so that the air can be humidified during normal power generation of the fuel cell 10.
In the present embodiment, the humidified air supply channel (oxidant gas supply channel) through which the humidified air (oxidant gas) supplied to the cathode 13 circulates is constituted by the pipe 31a (oxidant gas supply). Channel means).

The hydrogen sensor 32 is a type of sensor that detects hydrogen gas supplied to the anode 12 (counter electrode). The hydrogen sensor 32 is provided on the pipe 31a on the cathode 13 side when viewed from the on-off valve 42, and detects an actual hydrogen gas concentration (hereinafter, measured hydrogen gas concentration) in the pipe 31a. . The hydrogen sensor 32 is located downstream of the connection point J between the piping 31 a and the piping 41 of the scavenging gas introduction system 40 described later and upstream of the fuel cell 10.
Thereby, the hydrogen sensor 32 detects the hydrogen gas before passing through the on-off valve 42 and flowing into the fuel cell 10. That is, the hydrogen gas immediately after passing through the on-off valve 42 is quickly detected.

<Cathode system-Air discharge side>
The air discharge side of the cathode system 30 will be described. The air discharge port 13b communicating with the cathode 13 of the fuel cell 10 is connected to the diluter 26 via a pipe 31b. As a result, the cathode off-gas discharged from the air discharge port 13b (humidified air + generated water during normal power generation, scavenged gas + extruded water during scavenging) is supplied to the diluter 26 via the pipe 31b. It is like that.
The piping 31b is provided with a back pressure valve (not shown). By adjusting the back pressure, the pressure of hydrogen gas on the anode 12 side and the pressure of air on the cathode 13 side in the fuel cell 10 are adjusted. Are to be balanced. Thereby, the lifetime of the electrolyte membrane 11 is extended.

<Scavenging gas introduction system>
The scavenging gas introduction system 40 (connection system) is provided in the pipe 41 and a pipe 41 (connection path connecting the fuel gas supply path and the oxidant gas supply path) that connect the pipe 23a and the pipe 31a. And an open / close valve 42 (scavenging gas introduction means). The on-off valve 42 is electrically connected to the control unit 51, and the control unit 51 opens / closes the on-off valve 42. During normal power generation of the fuel cell 10, the on-off valve 42 is closed, and the gas flow in the pipe 41 is shut off. On the other hand, when scavenging the fuel cell 10, the on-off valve 42 is opened, and scavenging gas (non-humidified air) is introduced from the cathode system 30 to the anode system 20.

<ECU>
The ECU 50 includes a control unit 51 (control means, failure determination unit) and a control data storage unit 52 (failure determination data storage unit), which are a CPU, ROM, RAM, various interfaces, electronic circuits, various types. It consists of a storage medium.

[Control unit]
The control unit 51 is electrically connected to the shutoff valve 22, the compressor 31, and the on-off valve 42, and controls these as desired. The control unit 51 is electrically connected to the hydrogen sensor 32 and monitors the measured hydrogen gas concentration by the hydrogen sensor 32. Moreover, the control part 51 is electrically connected with the warning lamp 61 mentioned later, and turns ON / OFF the warning lamp 61 suitably. Further, the control unit 51 is connected to the IGSW of the fuel cell vehicle, and is linked to ON / OFF of the IGSW.

[Control unit-Failure judgment function]
The control unit 51 has a failure determination function for determining whether or not the on-off valve 42 has failed (S101 in FIG. 2). More specifically, when the fuel cell 10 normally generates power, when the closing command is issued to the on-off valve 42, the measured hydrogen gas concentration by the hydrogen sensor 32 and the predetermined hydrogen gas concentration in the control data storage unit 52 are calculated. In comparison, when “actually measured hydrogen gas concentration> predetermined hydrogen gas concentration”, it is determined that hydrogen gas passes through the on-off valve 42 and flows from the anode system 20 to the cathode system 30 and the on-off valve 42 is out of order. (FIG. 2, S101 / Yes).

[Control data storage unit]
The control data storage unit 52 stores a predetermined hydrogen gas concentration obtained by a preliminary experiment or the like. The predetermined hydrogen gas concentration is a reference hydrogen gas concentration for determining whether or not the on-off valve 42 is out of order when a close command is sent to the on-off valve 42. The control data storage unit 52 is electrically connected to the control unit 51, and the control unit 51 can appropriately refer to the predetermined hydrogen gas concentration.

<Others>
In addition, the fuel cell system 1A includes a warning lamp 61 provided on the instrument panel. The warning lamp 61 is electrically connected to the control unit 51, and the control unit 51 turns the warning lamp 61 on and off as appropriate.

≪Operation of fuel cell system≫
Next, with reference to FIG. 2 in addition to FIG. 1, the operation of the fuel cell 10 of the fuel cell system 1A during normal power generation will be described along with the flowchart set in the control unit 51. FIG. In addition, the control part 51 is performing the process of each step of the flowchart shown in FIG. 2 repeatedly.
Here, during normal power generation of the fuel cell 10, the IGSW of the fuel cell vehicle is turned on and the fuel cell system 1A is activated. During this normal power generation, the shut-off valve 22 is opened, hydrogen gas is sent from the hydrogen tank 21 to the anode 12, the compressor 31 is operated, and humidified air is sent from the operating compressor 31 to the cathode 13. Yes. On the other hand, the control unit 51 sends a close command to the on-off valve 42. Furthermore, here, a case where the pressure of hydrogen gas supplied to the anode 12 is higher than the pressure of humidified air supplied to the cathode 13 during normal power generation will be described.

In step S101, the control unit 51 determines whether or not the on-off valve 42 has failed.
Specifically, the control unit 51 compares the measured hydrogen concentration detected by the hydrogen sensor 32 with the predetermined hydrogen concentration stored in the control data storage unit 52, and “measured hydrogen gas concentration> predetermined hydrogen gas concentration”. In this case, it is determined that the on-off valve 42 has failed (S101, Yes), and the process proceeds to step S102.
On the other hand, when “actually measured hydrogen gas concentration ≦ predetermined hydrogen gas concentration” (S101, No), the process proceeds to return and then returns to start.

<Treatment due to opening / closing valve failure>
In step S102, the control unit 51 turns on the warning lamp 61. Thereby, the driver of the fuel cell vehicle can visually recognize that the on-off valve 42 is out of order.
At the same time, the control unit 51 closes the shut-off valve 22, turns off the compressor 31, and stops the fuel cell system 1A. Thereby, the power generation of the fuel cell 10 is stopped in a state where the hydrogen gas that has passed through the on-off valve 42 is supplied to the cathode 13. That is, the power generation of the fuel cell 10 is stopped under the situation where hydrogen gas exists on both sides of the electrolyte membrane 11, and the deterioration of the electrolyte membrane 11 and the like is prevented.

  Thereafter, the process proceeds to return and returns to start. Thereafter, for example, when the on-off valve 42 is maintained and becomes normal, the determination in step S101 is No, and the fuel cell 10 continues to generate electricity satisfactorily.

  As described above, according to the fuel cell system 1A according to the present embodiment, it is possible to detect a failure of the on-off valve 42 during normal power generation of the fuel cell 10, and to stop the power generation of the fuel cell 10 when a failure is detected. Thus, a device such as the electrolyte membrane 11 can be protected.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to the said embodiment, For example, it can change as follows in the range which does not deviate from the meaning of this invention.

  In the above-described embodiment, the case of the fuel cell system 1A in which the pressure of the hydrogen gas supplied to the anode 12 during the normal power generation of the fuel cell 10 is higher than the pressure of the humidified air supplied to the cathode 13 has been described. In the case of the fuel cell system 1B in which the pressure of the humidified air supplied to 13 is higher than the pressure of the hydrogen gas supplied to the anode 12, instead of the hydrogen sensor 32, as viewed from the on-off valve 42, as shown in FIG. An oxygen sensor 27 (gas detection means) is provided in the pipe 12a on the anode 12 side, and the actual oxygen gas concentration in the air that has flowed from the cathode system 30 through the on-off valve 42 and into the anode system 20 (hereinafter, measured oxygen gas concentration). ) Is detected. Needless to say, the oxygen gas is a gas to be supplied to the cathode 13 which is the counter electrode of the anode 12, and the oxygen sensor 27 is a type of sensor that detects oxygen gas.

  In this case, the control data storage unit 52 stores a predetermined oxygen gas concentration instead of the above-described predetermined hydrogen gas concentration. Then, as shown in FIG. 4, the control unit 51 compares the measured oxygen gas concentration with the predetermined oxygen gas concentration during normal power generation, and the case of “measured oxygen gas concentration> predetermined oxygen gas concentration” (FIG. 4). , S201, Yes), and set so as to determine that the on-off valve 42 is out of order.

  Further, when the oxygen sensor 27 is provided from the on-off valve 42 to the pipe 12a on the anode 12 side in this way, the control unit 51 sends an open command to the on-off valve 42 when scavenging the fuel cell 10. When oxygen gas is not detected by the oxygen sensor 27, the control unit 51 can determine that the on-off valve 42 has failed. Thereby, unscavenging of the anode 12 of the fuel cell 10 can be prevented.

  In addition, both the oxygen sensor 27 and the hydrogen sensor 32 are provided, and pressure sensors are provided in the piping 23a of the anode system 20 and the piping 31a of the cathode system 30, respectively, so that “the pressure of the anode system 20> the pressure of the cathode system 30”. In this case, the determination based on the hydrogen sensor 32 may be prioritized, and the determination based on the oxygen sensor 27 may be prioritized when “the pressure of the anode system 20 <the pressure of the cathode system 30”.

  In the above-described embodiment, the hydrogen sensor 32 is arranged in the pipe 31 a on the upstream side of the fuel cell 10. However, the hydrogen sensor 32 may be arranged in the pipe 31 b on the downstream side of the fuel cell 10. In addition, the hydrogen sensor 32 may be disposed in a pipe 41 between the connection point J and the on-off valve 42, or may be disposed in a pipe 31 a between the connection point J and the compressor 31. That is, it goes without saying that even if the hydrogen sensor 32 is located at such a position, it belongs to the technical scope of the present invention. The same applies to the oxygen sensor 27 described above.

  In the above-described embodiment, it is assumed that only the predetermined hydrogen gas concentration is stored in the control data storage unit 52. However, for example, the O-ring (seal member) incorporated in the on-off valve 42 is deteriorated (for example, the fuel cell 10). A plurality of predetermined hydrogen gas concentrations such as a first predetermined hydrogen gas concentration corresponding to a level at which power generation can be continued and a second predetermined hydrogen gas concentration corresponding to a level at which the on-off valve 42 is not completely closed may be stored. . Then, when “second predetermined hydrogen gas concentration> measured hydrogen gas concentration> first predetermined hydrogen gas concentration”, the control unit 51 does not immediately stop the fuel cell system 1A and travels to a place where the fuel cell vehicle can be maintained. On the other hand, when “measured hydrogen gas concentration> second predetermined hydrogen gas concentration”, the shutoff valve 22 may be closed, the compressor 31 may be stopped, and the fuel cell system 1A may be stopped.

It is a block diagram of the fuel cell system which concerns on this embodiment. It is the flowchart set to the fuel cell system which concerns on this embodiment. It is a block diagram of the fuel cell system which concerns on a modification. It is the flowchart set to the fuel cell system which concerns on a modification.

Explanation of symbols

1A, 1B Fuel cell system 10 Fuel cell 11 Electrolyte membrane 12 Anode 13 Cathode 20 Anode system 22 Shut-off valve 27 Oxygen sensor (gas detection means)
30 Cathode system 31 Compressor 32 Hydrogen sensor (gas detection means)
40 Scavenging gas introduction system 42 On-off valve 50 ECU
51 Control Unit 52 Control Data Storage Unit 61 Warning Lamp

Claims (2)

A fuel cell that generates power by supplying fuel gas to the anode and oxidant gas to the cathode; and
A fuel gas supply channel through which fuel gas supplied to the anode flows;
An oxidant gas supply channel through which an oxidant gas supplied to the cathode flows;
A connection channel connecting the fuel gas supply channel and the oxidant gas supply channel;
An on-off valve provided in the connection channel;
A gas detection means,
The fuel cell system according to claim 1, wherein the gas detection means is a sensor of a type that is located on at least one side of the anode and the cathode from the on-off valve and that can detect a gas supplied to the counter electrode.   The fuel cell system according to claim 1, wherein the gas detection unit is located upstream of the fuel cell.

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